With increasing awareness of potential damage to the environment resulting from recyclables directed to waste landfill dumps or incineration, more industries and municipalities are implementing waste diversion and recycling programs to significantly reduce the volume of waste that must be processed in a conventional manner. However, as the rate of waste diversion and recycling has increased, processing facilities have found that certain recyclables, in particular compostable materials, have increasingly become contaminated with synthetic materials such as fibers and plastics due to improper separation. Furthermore, undesirable stone and glass are often mixed with biodegradable materials when collected for recycling.
Municipal and industrial compost facilities in North America and in other jurisdictions are struggling with a growing contamination problem as they attempt to recycle biodegradable materials in an efficient and cost effective manner. A particular challenge is that there are stones, glass, and numerous types of synthetic materials such as fibers and plastics found in compost which are diverse in shape, size and density. Fibers may vary in shape, size and density, ranging from natural and synthetic textiles such as cotton, wool, burlap, polyester fiber and nylon from apparel, furniture, carpeting, rags, wipes, scrub pads, rope, string, etc. Plastics may vary considerably in shape, size and density, ranging from larger pieces of solid plastics, to thin strips of plastics torn from plastic bags and packaging. Furthermore, biodegradable material often has high moisture content, making effective separation of stone, fibers and plastics from the organic materials technically challenging. These technical challenges result in increased wear on processing machinery, increased labor and operating costs, and a reduction in the market value of the finished compost product. At worst, the processed compost may be so contaminated by that it is unusable altogether and must ultimately be discarded as waste, thereby defeating the purpose of diverting and recycling in the first place.
In U.S. Pat. No. 8,910,797, an earlier patent issued to the present inventor, a novel method and apparatus was disclosed for separating plastics from compost and other recyclable materials. While the method and apparatus described in the issued patent was effective for removal of a substantial amount of plastics contaminants, it was found that other types of contaminants such as stones, glass and other synthetic materials remained in the compost after processing.
Therefore, what is needed is a further improved method and apparatus for separating stones, glass, fibers and plastics contaminants from biodegradable materials that overcomes at least some of the limitations in the prior art.